An electroluminescence (EL) device includes: a transparent substrate; and a light emitting unit formed on the transparent substrate, where the light emitting unit includes a positive electrode, a negative electrode and a light emitting layer provided therebetween. When a voltage is applied between the electrodes, an electron and a hole, which serve as carriers, are injected into the light emitting layer and recombine with each other to generate an exciton, and thereby the EL device emit light.
In general, the EL devices can be classified into an organic EL device and an inorganic EL device. The organic EL device employs an organic material for a luminescence material (such as a fluorescent material and a phosphorescent material) of the light emitting layer. The inorganic EL device employs an inorganic material for a luminescence material. The organic EL device has advantages that: it can emit a high-brightness light with a low applying voltage; it can select various of emission colors by changing the types of luminescence materials; and it can be easily produced in a light emitting panel of planar shape. Because of these advantages, recently, the organic EL device is interested to be applied for a lighting apparatus.
The light emitting unit has a transparent electrode formed of ITO, which has a comparatively large in-plane resistance. Therefore, the potential gradient of the transparent electrode with respect to the light emitting layer becomes large. This causes a dispersion of brightness in a plane of the light emitting layer. In order to suppress such the dispersion of brightness, it has been developed such a planar light emitting device that includes a plurality of feeding electrodes for leading out the positive electrode and the negative electrode outward the light emitting panel. With this configuration, the potential gradient with respect to the light emitting layer can be lowered (for example, refer to Japanese patent application publication 2010-232286A).
FIGS. 7A and 7B show an example of a light emitting module employing such the planar light emitting panel. The light emitting module 101 includes: a light emitting panel 103 having a light emitting unit 102; a circuit board 104 for supplying electric power to the light emitting unit 102 of the light emitting panel 103; and a case unit 105 in which the light emitting panel 103 and the circuit board 104 are housed. In the light emitting module, a plurality of feeding electrodes (103a, 103b) are arranged along a periphery of the light emitting panel 103. Each of the plurality of feeding electrodes (103a, 103b) is electrically connected to either a positive electrode or a negative electrode of the light emitting unit 102. The case unit 105 includes a case body 150 and a cover 151. The light emitting panel 103 is supported by the case body 150. The cover 151 is arranged at a non-emitting side (at a reverse side to a side on which the light emitting panel 103 is arranged) of the case body 150. The cover 151 is adapted to protect the circuit board 104 and the like. Some of feeding electrodes from among the plurality of feeding electrodes (103a, 103b) are electrically connected to the circuit board 104 by wirings 107. The feeding electrodes having same polarity are connected one another by wirings 108.
When connecting these electrodes, a wire bonding method is adopted by which a wire formed of such as aluminum is used for the wiring. In general, in the wire boding method, the wiring (107, 108) is provided in an arch-shape to have some slack as shown in FIG. 8A in order to avoid a breaking of the wire caused of such as thermal expansion and contraction of the wire.
With regard to such a light emitting module, it has been desired to increase the light emitting area while streamlining the module shape. One way of increasing the light emitting area is to increase the dimension of the light emitting layer. In order to do so, the plurality of feeding electrodes are needed to be arranged at the periphery of the light emitting panel 103 as shown in FIG. 7A, 7B. However, when connecting, by the wirings 108 through the wire bonding method, the feeding electrodes 103a to each other and the feeding electrodes 103b to each other which are provided at the periphery of the light emitting panel 103, the module is required to have sufficient space for accommodating the wire (each of the wires is provided in an arch-shape). Therefore, as shown in FIG. 8A, the cover 151 of the module is required to be designed to have a predetermined thickness (sufficient “height”) at the periphery thereof. In this configuration, a user is likely to feel that the module is comparatively thick (user is likely to receive a thickness impression). In order to suppress such the thickness impression, periphery of the cover 151 may be chamfered. However in this case, as shown in FIG. 8B, the wiring 108 possibly comes into contact with the inner surface of the cover 151 to be damaged.